1. Field of the Invention
The invention relates to a device for automatically ejecting a workpiece chucked to a spindle in a machine tool, in particular, to such a workpiece ejecting device for the machine tool, which can smoothly eject the workpiece by means of separate ejecting operation without any affection from the rotation of the spindle.
2. Background of the Related Art
In general, a spindle of the machine tool (for example, an NC lathe and the like) is provided at opposite side of a main spindle to perform cutting work of a workpiece, and the cutting worked workpiece is ejected automatically from a chuck by means of ejection operation of the ejecting device.
The conventional ejecting device for the spindle for automatically ejecting the workpiece is shown in FIG. 5 showing an assembling section of the conventional spindle assembly. As shown in the drawing, a chuck 16 is mounted at the spindle 14 to clamp the workpiece. The chuck 16 is connected to a front end of a drawing tube 18. A rear end of the drawing tube 18 is positioned at rear side of the spindle 14 so that it is connected to a chucking cylinder 22 for clamping/unclamping the chuck 16. Also, a workpiece ejecting rod 20 is positioned within the drawing tube 18 to discharge the workpiece. The workpiece ejecting rod 20 is connected to an ejecting cylinder 23 positioned at rearward lower side of the chucking cylinder 22 so that it can move forward and rearward. A front end of the workpiece ejecting rod 20 is supported by the drawing tube 18 by means of an inner guide 5, and also a rear end of the workpiece ejecting rod 20 is rotatably supported by means of a bearing 6.
Accordingly, the ejecting operation of the workpiece is progressed as follows after the machined workpiece has been clamped to the chuck 16.
At first, the drawing tube 18 is moved forward by the operation of the chucking cylinder 22 to unclamp the chuck 16. Then, the ejecting cylinder 23 is operated to move forward a locater 21 connected to the workpiece ejecting rod 20 to push and eject the workpiece. In this case, the front end of the workpiece ejecting rod 20 is supported by the sliding movement of an oil seal 62 installed at an outer peripheral surface of the inner guide 5 along an inner peripheral surface of the drawing tube 18.
Meanwhile, when the spindle 14 is rotated by the rotation drive of a pully 13 during the machining of the workpiece, the ejecting rod 20 also rotates via the drawing tube 18 and the inner guide 5. In this case, the ejecting rod 20 rotates with eccentric while being supported by the bearing 6 installed at rear end thereof.
At this time, the ejecting rod 20 rotates eccentrically with while being supported by the rear side bearing 6. In addition, when the spindle rotates at high velocity above 5,000 rpm, the ejecting rod 20 produces vibration, noise and heat to thereby cause bending deformation of the ejecting rod 20. Also, when the ejecting rod 20 moves forward and rearward, it may be caught between the bearings 6 to cause malfunction of the ejecting operation.
Furthermore, as the ejecting cylinder 23 is configured to be an eccentric axis operation structure so that it can push or pull the workpiece ejecting rod 20 by means of a bracket 25 with it strayed out of the axial moving line of the spindle 14, malfunction can be easily brought about at the time of the ejecting operation of the ejecting rod 20.